Inhibition of GPR4 Ameliorates Neuropathic Pain and Neuronal Ferroptosis via Regulation of Spinal RhoA/YAP Signaling in Rats.

Neuropathic pain is a chronic pain disorder refractory to conventional analgesics. Iron-dependent neuronal ferroptosis has been implicated in its pathogenesis. G protein-coupled receptor 4 (GPR4), a proton-sensing receptor, is involved in inflammation and ferroptosis, but its role in neuropathic pain and spinal neuronal ferroptosis remains unclear. Neuropathic pain was induced in rats using the spared nerve injury (SNI) model, and GPR4 expression and its effects on pain behaviors, neuronal ferroptosis, and spinal inflammation were examined. GPR4 was inhibited by a selective antagonist or small interfering RNA (siRNA), while Ras homolog family member A (RhoA) and Yes-associated protein (YAP) were activated via intrathecal injection of specific agonists. Spinal GPR4 expression was significantly upregulated and neuronal ferroptosis was induced by SNI, as evidenced by increased iron accumulation, lipid peroxidation, and dysregulated ferroptosis-related protein expression. SNI-induced mechanical allodynia, cold hyperalgesia, neuronal ferroptosis, and spinal inflammation were attenuated by GPR4 inhibition or knockdown. Mechanistically, the spinal RhoA/YAP signaling pathway was activated by SNI, and this activation was reversed by GPR4 inhibition. Furthermore, the analgesic and anti-ferroptotic effects of GPR4 inhibition were abolished by RhoA or YAP activation. It is demonstrated that GPR4 regulates neuropathic pain, neuronal ferroptosis, and spinal inflammation via the spinal RhoA/YAP signaling pathway, suggesting that GPR4 inhibition may represent a promising novel therapeutic strategy for neuropathic pain.